I think you may be a little confused about the idea of "drive" The MoFo is a very easy load, so a passive will drive it perfectly well. What you are missing is gain, not drive (assuming we agree drive means the ability to work into a low impedance or reactive load). The MoFo has a voltage gain of just about 1. So if you need 1W RMS into your 8 ohm speakers, it will need to produce a output voltage of 2.82v RMS. So the MoFo will need a input voltage of 2.82v RMS. Assuming you have a CD as a source that will nominally produce a output voltage of 2v RMS, you will need to multiply the voltage to get to 1W out.But, as I have other pre's it would be nice if they were capable of driving the MoFo's as well
From that you can work out what gain you need or want. All the talk of "drive" is just confusing matters.